Peter KriPeter Križan -
Transcript of Peter KriPeter Križan -
Novel sensors for Cherenkov counters
Peter KrižanPeter KrižanUniversity of Ljubljana and J. Stefan Institute
Advanced Instrumentation Seminar,Advanced Instrumentation Seminar, SLAC, June 10, 2009
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Contents
Why particle identification?
Ring Imaging CHerenkov countersRing Imaging CHerenkov counters
Novel photon sensors: HAPD, MCP PMT, G-APD
Summary and outlook
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Why particle ID?
Example 1: B factoryWithout PID Example 1: B factory
Particle identification reduces the fraction ofreduces the fraction of wrong Kπ combinations (combinatorial(combinatorial background) by ~6x
With PID
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Why particle ID?
Example 2: HERA-BWithout PID
Example 2: HERA B
K+K- invariant mass.
The inclusive φ K+K-
decay only becomes visible after particle identification is taken into accountWith PID
K+K- invariant mass (GeV)
account.With PID
φ K+K-
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Why particle ID?
Example 3: LHCb(MC prediction)(MC prediction)
Need to distinguish Bd ππ from other similar topology 2-body decays
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Why particle ID?
Particle identification at B factories (Belle and BaBar): was essential for the observation of CP violation in the B
B0
meson system.
B0_B
B0 and its anti-particle decay differently to they ysame final state J/ψ K0
Flavour of the B: from decay products of the other B:products of the other B: charge of the kaon, electron, muon
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
muon
particle ID is compulsory
Why particle ID?
PID is also needed in:
•Spectroscopy of charmonium and charmonioum like states
•Spectroscopy of charmed hadrons
•Searches for exotic hadronic states
•Searches for exotic states of matter (quark-gluon plasma)
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Example: Belle
Aerogel Cherenkov Counterμ and KL detection system
(14/15 layers RPC+Fe)(n=1.015-1.030)
Silicon Vertex Detector3.5 GeV e+
Silicon Vertex Detector(4 layers DSSD)
Electromag. Cal.(CsI crystals, 16X0)( y , 0)
Central Drift Chamber(small cells, He/C2H6)
8 GeV e-
ToF counter1.5T SC solenoid
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Particle identification systems in Belle
Aerogel Cherenkov Counterμ and KL detection system
(14/15 layers RPC+Fe)(n=1.015-1.030)
Silicon Vertex Detector3.5 GeV e+
Silicon Vertex Detector(4 layers DSSD)
Electromag. Cal.(CsI crystals, 16X0)( y , 0)
Central Drift Chamber(small cells, He/C2H6)
8 GeV e-
ToF counter1.5T SC solenoid
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Identification of charged particlesParticles are identified by their mass or by the way they
interact. Determination of mass: from the relation between
momentum and velocity, p=γmv. Momentum known( di f t i ti fi ld)(radius of curvature in magnetic field)Measure velocity:
time of flighttime of flightionisation losses dE/dxCherenkov photon angle (and/or rate)Cherenkov photon angle (and/or rate)transition radiation
Mainly used for the identification of hadrons.Mainly used for the identification of hadrons.
Identification through interaction: electrons and muons
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
g
Cherenkov radiation
A charged track with velocity v=βc exceeding the speed of light c/n in a medium with refractive index n emits polarized / plight at a characteristic (Cherenkov) angle, cosθ = c/nv = 1/βnβ
(c/n) t
Two cases:β < βt = 1/n: below threshold no Cherenkov light is emitted.
v t
β βt / gβ > βt : the number of Cherenkov photons emitted over unit
photon energy E=hν in a radiator of length L:
θθα 2112 sin)()(370sin LeVcmLdN −−== F d t t d h t
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
θθ sin)()(370sin LeVcmLcdE
==h Few detected photons
Measuring Cherenkov angle
Idea: transform the directioninto a coordinateinto a coordinatering on the detection plane
Ring Imaging CHerenkovRing Imaging CHerenkov
Proximity focusing RICH
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
RICH with a focusing mirror
Measuring Cherenkov angle
ring radius on thering radius on the detection plane
Cherenkov angle
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Cherenkov angle
Photon detection in RICH counters
RICH counter: measure photon impact point on the photon detector surfacephoton detector surface detection of single photons with
• sufficient spatial resolution• sufficient spatial resolution• high efficiency and good signal-to-noise ratio• over a large area (square meters)• over a large area (square meters)
Special requirements:p q• Operation in magnetic field• High rate capabilityg p y• Excellent timing (time-of-arrival
information)
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Belle upgrade Belle-II
SC solenoidCsI(Tl) 16X0
pure CsI (endcap)1.5T pure CsI (endcap)Aerogel Cherenkov counter+ TOF counter
“TOP” or DIRCμ / KL detection
TOP or DIRC
+ Aerogel RICH14/15 lyr. RPC+Fe
tile scintillator
Tracking + dE/dxsmall cell + He/C Hsmall cell + He/C2H5
remove inner lyrs.fast gas+Si r<20 cm
New readout and computing
Si vtx. det.4 lyr. DSSD
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
computing systems
2 pixel/striplet lyrs. + 4 lyr. DSSD
Present Belle: threshold Cherenkov counterACC (aerogel Cherenkov counter)( g )
K (below threshold) vs. π (above) by properly choosing n for a given kinematic region (more energeticn for a given kinematic region (more energetic particles fly in the ‘forward region’)
Detector unit: a block of aerogel and two fine-mesh PMTs
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Fine-mesh PMT: works in high B fields
Belle ACC : threshold Cherenkov counter
expected yield vs p NIM A453 (2000) 321
yield for 2GeV<p<3 5GeV:yield for 2GeV<p<3.5GeV:expected and measured number of hitsnumber of hits
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Belle upgrade – side view
Two new particle ID devices, both RICHes:
Barrel: TOP or focusing DIRC
Endcap p o imit foc sing RICH
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Endcap: proximity focusing RICH
Endcap: Proximity focusing RICHK/π separation at 4 GeV/c:θc(π) ~ 308 mrad (n = 1.05)c( ) ( )θc(π)– θc(K) ~ 23 mrad
For single photons: δθc(meas.)=σ0 ~ 14 mrad,typical value for a 20mm thicktypical value for a 20mm thick
radiator and 6mm PMT pad size0σσPer track:pe
track N0σ =
Separation: [θc(π)–θc(K)]/σtrack
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
5σ separation with Npe~10
Beam tests
pion beam (π2) at KEK
Clear rings, little backgroundClear rings, little background
Photon detector: array of 16 H8500 PMTs
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
16 H8500 PMTs
Beam test: Cherenkov angle resolution and number of photonsresolution and number of photons
Beam test results with 2cm thick aerogel tiles: 4 K/ i
NIM A521(2004)367; NIM A553(2005)58
>4σ K/π separation
σ0~ 15mrad
Npe~6
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Number of photons has to be increased.
Radiator with multiple refractive indices
How to increase the number of photonswithout degrading the resolution?
refractive indices
stack two tiles with different refractive indices: “focusing” configurationnormal
n1< n2n1= n2
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljanafocusing radiator
Focusing configuration – data
4cm aerogel single index
2+2cm aerogel2+2cm aerogel
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, LjubljanaNIM A548 (2005) 383
Radiator with multiple refractive indices
Such a configuration is only possible with aerogel (a form of SixOy)– material with a tunable refractive index between 1.01 and 1.13.
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Photon detectors for the aerogel RICHrequirements and candidatesrequirements and candidates
Need: Operation in a high magnetic field (1.5 T)Pad size ~5-6mm
One of the candidates: large active area HAPD of the proximity focusing type g
Multialkaliphotocathode
-10kV e
p
-10kV15~25mm
e-
Pi l APD HAPD R&D project inPixel APD HAPD R&D project in collaboration with HPK.
Long development time
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Finally enough working samples for a beam test at KEK last spring
NIM A595 (2008) 180
Photon detector candidate: HAPD beam test
• test with 2 GeV/c electrons @ KEK• detected number of photons: ~ 6• Cherenkov angle resolution: ~ 13mrad• large background due to the Cherenkov photons produced in the HAPD window• second ring due to reflection on APD
Better than 4σ π/K separation @ 4GeV/c
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Open issues: long term stability and neutron irradiation damage – both under study
MCP-PMT
Photon detector candidate: BURLE/Photonis MCP-PMT
BURLE 85011 microchannelplate (MCP) PMT: multi-anode
MCP PMT
p ( )PMT with two MCP steps
multi-anode PMTs
good performance in beam andbench tests NIMA567 (2006) 124
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
bench tests, NIMA567 (2006) 124very fastopen issue: ageing
BURLE/Photonis MCP-PMT
BURLE 85011 microchannel plate (MCP) PMT: excellent timeresolution after time walk correction
σ = 40ps σ = 37ps
T il b i ifi tlTails can be significantly reduced by:
•increased cathode-MCP•increased cathode-MCP voltage difference
• decreased
σ = 38psσ = 39psphotocathode-MCP distance
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Geiger-APDs as photon detector?Can we use SiPMs (Geiger mode APDs) as the photon detector in a RICH counter?
+immune to magnetic field
+high photon detection efficiency single photon sensitivity+high photon detection efficiency, single photon sensitivity
+easy to handle (thin, can be mounted on a PCB)
+potentially cheap (not yet...) silicon technology
+no high voltage+no high voltage
-very high dark count rate (100kHz – 1MHz) with single photon pulse height
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
-radiation hardness
SiPMs as photon detectors?SiPM is an array of individual APDs operating in Geiger mode; a resistor is used to quench the pulse. Characteristics:
low operation voltage ~ 10-100 V gain ~ 106
peak PDE up to 65%(@400nm) 1 mmpeak PDE up to 65%(@400nm)PDE = QE x εgeiger x εgeoεgeo – dead space between the cells
100U
1 mm
gtime resolution ~ 100 pswork in high magnetic fielddark counts ~ few 100 kHz/mm2
050U
100U
dark counts ~ few 100 kHz/mmradiation damage (p,n) 025U
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Hamamatsu MPPC: S10362-11
Surface sensitivity for single photons
• 2d scan in the focal plane of the laser beam (σ ≈ 5 μm)( μ )
• intensity: on average << 1 photon• Selection: single pixel pulse height, in
a 10 ns indoa 10 ns window
5 t i Cl 1 t i5 μm step size Close-up: 1 μm step size
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Time resolution after time walk correction
Time resolution
E407
E407 S137 H100C H050C H025C
Time resolutiontime(ps)time(ps)
σred (ps) 127 182 145 212 154σblue (ps) 97 151 136 358 135
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
• σ ≈ 100-200 ps • σred > σblue
Can such a detector work?
Improve the signal to noise ratio:
•Reduce the noise by a narrow (<10ns) time window
•Increase the number of signal hits per single sensor by using g p g y glight collectors and by adjusting the pad size to the ring thickness
E.g. light collector with reflective walls
SiPM
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
or combine a lens and mirror walls
PCB
Expected number of photons for aerogel RICH
with multianode PMTs or SiPMs(100U), andaerogel radiator: thickness 2.5 cm, n = 1.045
nm
aerogel radiator: thickness 2.5 cm, n 1.045and transmission length (@400nm) 4 cm.
incident photons/10nm
oton
s/10
n
NSiPM/NPMT~5
Assuming 100% detectorSiPM photons
phoAssuming 100% detector
active area
N=76
PMT photons
N=15Never before tested in a RICH where we have to detect single photons
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
λ[nm]we have to detect single photons. Dark counts have single photon pulse heights (rate 0.1-1 MHz)
Cosmic test setup
scintillation counter
MWPC telescope
2 5 l 1 0456 Hamamatsu SiPMs used:
2x 100U; background ~400kHz
2.5cm aerogel n=1.045
2x 050U; background ~200kHz2x 025U; background ~100kHz
signals amplified (ORTEC FTA820)multianode PMTs SiPMs signals amplified (ORTEC FTA820),discriminated (EG&G CF8000) andread by multihit TDC (CAEN V673A)
multianode PMTsarray 2x6
SiPMsx6
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
with 1 ns / channel
SiPM: Cherenkov angle distributions for 1ns time windows
-3 ns-4 ns-5 ns-6 ns
ΘcΘcΘcΘc
+1 ns-2 ns 0 ns-1 ns
cc
ΘcΘcΘcΘc
+5 ns+4 ns+3 ns+2 ns
ΘcΘcΘcΘc
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Cherenkov photons appear in the expected time windowsFirst Cherenkov photons observed with SiPMs!
SiPM Cherenkov angle distribution
scintillation counterscintillation counter
MWPC SiPMs signaltelescope
2.5cm aerogel n=1.045
→ SiPMs give 4 x more photonsthan PMTs per photon detector
Θc
than PMTs per photon detectorarea – in ~ agreement withexpectations
multianode PMTsarray 2x6
SiPMsx6
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
N.B. Signal/noise should improve by x3 with better tracking!
Detector module design
2.5mmSiPM array with light guides
4.3mm
1
10o
1mm
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, LjubljanaA multi-channel module prepared for a beam test at CERN
Light guide geometry optimisation
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Light guide geometry optimisation
Light guide length optimisation
Light guide – SiPM gap
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljanad (mm)
gap (mm)
Detector module for beam tests at KEK
SiPMs: array of 8x8 SMD mount Hamamatsu S10362-11-100PHamamatsu S10362 11 100Pwith 0.3mm protective layer
Light guidesLight guides
SiPMsSiPMs
2cm
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, LjubljanaSiPMs + light guides
Photon detector for the beam test
SiPMs: array of 8x8 SMD mount Hamamatsu S10362-11-100Pwith 0 3mm protective layerwith 0.3mm protective layer
64 SiPMs
20mm20mm
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Fully assembled detector module
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
SiPM beam test: TDC distributions
•Total noise rate ~35 MHz (~600 kHz/MPPC)•Hits in the time window of 5ns around the peak are selectedHits in the time window of 5ns around the peak are selected for the Cherenkov angle analysis
without light guides with light guides
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
SiPM beam test: Cherenkov angle distributionsdistributions
without light guides
on-time hits
ff ti hitoff-time hits
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, LjubljanaBackground-subtracted distributions
discrepancy with PDE valuesdiscrepancy with PDE values as given by the producer, observed also by other groups
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Can such a detector work?
Using all the tricks, the background occupancy will still be high.
HERA-B RICH eventp y g
Experience from HERA-B RICH:Experience from HERA B RICH: successfully operated in a high occupancy environment (up to 10%).
Need >20 photons per ring (had ~30) for a reliable PID.
K K p Kπ K
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
PID efficiency vs occupancyK identification efficiency at 1% π missid. probability for different number of photons per ring vs background level
40MHz
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Again OK if the number of photons >20
Summary of tests
We have proven that SiPMs can be used as single photon sensors in Ring g p gImaging Cherenkov (RICH) counters.
Light guides improved signal/noise.
The sensor is easy to operate, robust.
The number of photons is high enough to allow for sufficient kaon/pion separation even at high dark count rates.
Can we use it in Belle-II?Can we use it in Belle II?
•Cost
•Radiation damage
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
•Radiation damage
Radiation damage
Becomes very hard to operate aboveBecomes very hard to operate above the neutron fluence of 1011 n cm-2
Expected fluence in at Belle-II at 50/ab: 2-20 1011 n cm-2
Worst than the lowest line
Very hard to use the presently available SiPMs as single photon detectors e y a d to use t e p ese t y a a ab e S s as s g e p oto detecto sfor the whole lifetime of a Super B factories because of radiation damage by neutrons
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Also: could only be used with a sofisticated electronics – wave-form sampling
Read out: Buffered LABRADOR (BLAB1) ASIC( )Gary Varner, Larry Ruckman (Hawaii)
Successfully flew on ANITA in Dec 06/Jan 07 (<= 50ps timing)
d h f CBeing used in the focusing DIRC tests at SLAC
• 64k samples deep
3mm x 2.8mm, TSMC 0.25um
• 64k samples deep• Multi-MSa/s to Multi-GSa/s
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
SummaryParticle identification is an essential part of several experiments, and has
contributed substantially to our present understanding of elementary particles and their interactions Techniques based on Cherenkov radiationparticles and their interactions. Techniques based on Cherenkov radiation have become indispensable for PID.
l h d b d l d f h hNovel photo-detectors are being developed for operation in high magnetic fields. They will play an essential role in the next generation of B physics experiments at Super B factories, as well as at hadron structure
i texperiments.
Geiger mode APDs (SiPMs) have been demonstrated to work well as single g ( ) gphoton detectors in spite of the high dark count rates.
Radiation damage of the available devices is at present limiting their use inRadiation damage of the available devices is at present limiting their use in Super B factories.
A i t ti li ti f SiPM i till ti li ht f PET
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
A very interesting application of SiPMs as scintillation light sensors for PET imaging is opening a new field of research.
PET: positron emission tomography
Beta+ emitters (e.g. radioactive fluor) produce two collinear gamma rays. These gamma rays are detected by a combination of a scintillation crystal and a photo-sensor. From the lines given by the hit pairs, the source distribution is reconstructed.
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
PET with SiPMs
Traditionally, PMTs are used as light sensors for PET scanners.
SiPMs: much smaller, no high voltage needed, works in high magnetic fields (several T).
photocathode dynodes anode
γ raye
scintillator PMT
SiPM
γ ray electric pulsePMTγ ray
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljanaelectric pulse
scintillator
PET with SiPMsThe use SiPMs could allow for a dual modality imaging – at the same time perform magnetic resonance (MRI) and PET imaging – an
MRI
p g ( ) g gimportant improvement for a faster and better diagnostics!
PET
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
PET
PET with SiPMs: tests
Test PET modules with:4x4 arrays of LYSO crystals (4.5 x 4.5 x 20(30) mm3)y y ( ( ) )16 SiPMs (Photonique 2.1x2.1 mm2)16 SiPMs (Hamamatsu 3x3 mm2)
Also interesting: SiPMs have a fast response (~100ps rms)fast response (~100ps rms)
important for TOF-PET
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Back-up slides
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Photon detectors for the aerogel RICH
Needs:• Operation in high magnetic field (1 5T)• Operation in high magnetic field (1.5T)
• High efficiency at λ>350nm Pad size 5 6mm• Pad size ~5-6mm
Candidates: l H(A)PD f h i i f i• large area H(A)PD of the proximity focusing type
• MCP PMT (Burle 85011)
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
• SiPMs
MCP PMT timing
Tails can be significantly d d breduced by:
• decreased photocathode-MCP distance and
•increased voltage differenceg
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
MCP PMT: Gain in magnetic field
Gain as a function of magnetic field for different operation voltagesand as a function of applied voltage for different magnetic fields...
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, LjubljanaMore talks on MCP PMTs during this workshop – W. Plass and A. Lehmann
MCP PMT: sensitivity
Number of detected hits on i di id l h lindividual channels as a function of light spot position.
B = 0 T, HV = 2400 VHV = 2400 V
B = 1.5 T, HV = 2500 V
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
In the presence of magnetic field, charge sharing and cross talk due to long range photoelectron back-scattering are considerably reduced.
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
TOF capability of a RICH
With a fast photon detector (MCP PMT), a proximity focusing RICH
b d l i f
2GeV/c π/K: Δt ~ 180ps
counter can be used also as a time-of-flight counter.
Time difference between π and K 4GeV/c π/K: Δt ~ 45ps
For time of flight: useCherenkov photonsfrom aerogel
track
STARTFor time of flight: use Cherenkov photons emitted in the PMTemitted in the PMT window
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Cherenkov photonsfrom PMT window
MCP-PMTaerogel
TOF capability: window photons
Expected number of detected Cherenkov photons emitted in the PMT window (2mm) is ~15the PMT window (2mm) is 15
Expected resolution ~35 ps
TOF test with pions and protons at 2 GeV/c.Distance between start counter and MCP-PMT is 65cm
In the real detector ~2m 3x better separation
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, LjubljanaNIM A572 (2007) 432
Time-of-flight with photons from the PMT window
Benefits: Čerenkov threshold in glass (or quartz) is much lower than in aerogel
Cherenkov angle aerogel n=1 05A l k
lower than in aerogel.
aerogel, n 1.05Aerogel: kaons (protons) have no signal below 1 6 GeVsignal below 1.6 GeV (3.1 GeV): identification in the veto mode.
Wi d h h ld f k ( ) i
Threshold in the window: π K p
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Window: threshold for kaons (protons) is at ~0.5 GeV (~0.9 GeV): positive identification possible.
Timing with a signal from the second MCP stageMCP stage
If a charged particle passes the PMT window, ~10 Cherenkov photons are detected in the MCP PMT; they are distributed over several anode channels.
Idea: read timing for the whole MCP second stage output
; y
gdevice from a single channel(second MCP stage), while 64 anode channels are used for σ < 40 psanode channels are used for position measurement
σ < 40 ps
Timing resolution as a function of
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
glight intensity
Burle MCP PMT beam test
● BURLE MCP-PMT mounted together with an array of 12(6x2) Hamamatsu R5900-M16 PMTs at 30mm pitch (reference counter)
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
MCP-PMTPhoton detector candidate: MCP-PMT
BURLE 85011 MCP-PMT:● multi-anode PMT with two MCP steps25 μm pores● 25 μm pores
● bialkali photocathode● gain ~ 0.6 x 106
ff %
multi-anode PMTs
● collection efficiency ~ 60%● box dimensions ~ 71mm square● 64(8x8) anode pads ● Tested in combination with multi-anode PMTs
● pitch ~ 6.45mm, gap ~ 0.5mm● active area fraction ~ 52%
● σϑ~13 mrad (single cluster)● number of clusters per track N ~ 4.5● σϑ~ 6 mrad (per track)ϑ●-> ~ 4 σ π/K separation at 4 GeV/c
● 10 μm pores required for 1.5T● 10 μm pores required for 1.5T● collection eff. and active area fraction should be improvedaging study should be carried out
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
● aging study should be carried out
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Can such a detector work?MC simulation of the counter response: assume 1mm2 active area SiPMs with 0.8 MHz (1.6 MHz, 3.2 MHz) dark count rate, 10ns time window
K identification efficiency at 1% π missid. probability
ε vs. pt 4 G V/ε at 4 GeV/c vs.
pad size
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
For different background levels
SiPM Photon Detection Efficiency (PDE)
Photons with short wavelengths will be absorbed in the very first layer of Si and create there an electron-hole pair.
In a structure with a n-type substrate (right) the electrons drift towards the high field of the p-n junction and trigger with high probability a breakdown A G-
25
30
35
%]
with high probability a breakdown. A G-APD made on a n-type substrate will be preferential sensitive for blue light.
A G-APD made on a p-type substrate
0
5
10
15
20
350 450 550 650 750
Wavelength [nm]
PDE
[%
A G-APD made on a p-type substrate (left) needs long wavelengths for the creation of electrons in the p-layer behind the junction and will have the
Photonique/CPTA Hamamatsu (SSPM_0710G9MM) (PSI-33-050C)
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
peak sensitivity in the green/red.
D. Renker, RICH Workshop, Giessen, May 2009
Surface sensitivity for single photons
• 2d scan in the focal plane of the laser beam (σ ≈ 5 μm)i t it 1 h t• intensity: on average << 1 photon
• Selection: single pixel pulse height, in TDC 10 ns window
S1375 μm step size Close up: 1 μm step sizeS1375 μm step size Close up: 1 μm step size
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Surface sensitivity for single photons 2
E407
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Surface sensitivity for single photons 3
H050C H025C
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Resolution per trackSingle photon resolution
Number of detected photons
Multilayer extensionsSingle photon resolution photons
Npe
σ0
petrack N
0σσ =
Cherenkov angle resolution per track:around 4.3 mrad
pe
around 4.3 mradπ/K separation at 4 GeV: >5σ
Several optimisation studies:Several optimisation studies:
Križan et al NIMA 565 (2006) 457
B k t l NIMA 553 (2005) 70
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
Barnyakov et al NIMA 553 (2005) 70
Aerogel productionTwo production centers: Boreskov Institute of Catalysis,
Novisibirsk, and KEK+Matsushita,
Considerable improvement in aerogel production methods:Considerable improvement in aerogel production methods: • Better transmission (>4cm for hydrophobic
and ~8cm for hydrophylic)y p y )• Larger tiles (LHCb: 20cmx20cmx5cm)• Tiles with multiple refractive indexp
20cmn1=1.046
n2=1.041
June 10, 2009 Advanced Instrumentation Seminar, SLAC Peter Križan, Ljubljana
n3=1.037